Fish sauces or fish fermented products are widely consumed as seasonings or cooking aid in Asian countries such as Japan, China and Southeastern countries such as Vietnam, Cambodia, Thailand and others. They are also widely consumed in Europe and North America. Fish sauces or fish fermented products are traditionally prepared through the fermentation of fish in the presence of salt.
The traditional method of preparation is usually based on a process involving autohydrolysis by endogeneous enzymes from fish. Such process requires a fermentation period of about 6 to 12 months to obtain an acceptable yield and sensory properties. In view of the relatively long production time, there have been many strategies, solutions or alternatives being proposed to reduce the production time.
One of the proposed methods is by adding hydrochloric acid to hydrolyse protein by which the time required is reduced to only a few hours. However, such process resulted in inferior flavour. Products that were produced by such method have very little aroma and taste and in most cases, some chloro-compounds may arise from the acid process.
Another proposed method for fish sauce production is by adding enzyme-rich components to accelerate the protein hydrolysis. Plant enzymes such as bromelain from pineapple stems or papain from unripe papaya have been used as addition. Although fish sauce can be recovered after 3 to 4 weeks, the characteristic and particularly the flavour of the finished product is inferior to the traditional fish sauce. A major problem that has arisen is that such product is generally accompanied by intense bitterness.
On the other hand, high amount of salt is added in the traditional method used to produce fish sauces or fish fermented products. The high salt concentration strongly inhibits the activities of most of the proteolytic enzymes. As such, the fish sauce produced under high salt concentration is far from optimal. Furthermore, as a substantial long period of time is required for preservation in salt solution and degradation, the salt contents in the final product is considerably high. Hence, many processes, solutions and alternatives have been proposed with the objectives of resolving the above problems.
Japanese patent application no. 2003-319944 tries to reduce the use of salt by producing a seasoning material under a highly sterilised condition. This application discloses a seasoning material obtained by mixing sterilised residue from dried fish extraction with a solid koji produced under sterilised condition, and degrading the mixture in the sterilised salt-free state. In this invention, residue from dried fish extraction is used as one of the main materials in the production of the seasoning material. The residue from dried fish extraction is a by-product from the dried fish processing factory. While the nutrients of the residue from dried fish extraction are lost during extraction, it also provides a poor flavouring power. In addition, although the process as disclosed in the application is a salt-free process, the process needs to be performed in a completely sterilised condition from the beginning step of preparing the residue from dried fish extraction, preparing koji, to the step of degrading the mixture of sterilised residue from dried fish extraction and koji. Sterilisation may increase the cost and level of difficulties involved in the production. Further, sterilisation may also overheat the food product which will therefore impair the organoleptic properties of the food products produced thereby.
In addition, the fish sauce produced through the traditional method possess a fishy flavour and unpleasant odour. The fishy flavour and unpleasant odour are sometime limiting the acceptability of consumers and such fish sauce may also be impairing the taste of food rather than enhancing it. In order to overcome these problems, various methods to reduce the fishy flavour and unpleasant odour have been proposed. International patent publication no. WO2004045310 discloses a process for the preparation of fish sauce by removing the gastro-intestine tract, and the fish flesh is mixed with ginger and tamarind before fermentation in order to reduce the fishy smell. However, this proposed method is not capable of effectively removing the undesirable odour of products but at that same time, it increases the production costs where other materials need to be prepared and added to the fish fermentation and further steps also need to be taken. Moreover, if the discarded internal organs are not disposed off in a proper way, it may become a potential environmental hazard. This is more acute when the amount of the discarded internal organs is normally quite considerable as huge amount of fish are needed since it is the main material in the production.
The conventional methods for preparing fish sauce are generally intended to produce liquid seasonings and therefore the methods are designed in such a way that the fermented product needs to undergo a pressing process to separate the liquid portion from the solid portion and only liquid portion of the fermented products are usable as seasonings. Usually, the solid portion is deemed unsuitable or unacceptable to be used or reproduced as a food composition.